Material handling apparatus with &#34;float&#34; accommodations to ground



Oct. 29, 1968 w. K. BROWN 3,407,953

MATERIAL HANDLING APPARATUS WITH "FLOAT" ACCOMMODATIONS TO GROUND Filed March 15, 1967 B l 9 3 4 4 F 4 7 k 4 4 D N in, TU U\, 4 T B 0 L Q F F D 8 m r--. mL w. Q 3 w INVENTORO WILBURN KELLY BROWN Qa wv; MA W United States Patent 3,407,953 MATERIAL HANDLING APPARATUS WITH FLOAT ACCOMMODATIONS TO GROUND Wilburn Kelly Brown, Morton Grove, Ill., assignor to Pettibone Mulliken Corporation, Chicago, 11]., a corporation of Delaware Filed Mar. 15, 1967, Ser. No. 623,362 1 Claim. (Cl. 214-770) ABSTRACT OF THE DISCLOSURE When a load-handling element such as a fork-lift device is carried by a vehicle in a manner to be raised and lowered hydraulically and also to be titled hydraulically, it can be made to accommodate itself to the contour of the ground along which it is to advance, by providing a float position in the lift and tilt valves.

Introduction The invention, of which the present disclosure is offered for public dissemination in the event adequate patent protection is available, relates to mobile material handling apparatus such as rough terrain fork-lift trucks and rough terrain front-end loaders.

Sometimes in the operation of devices of this character, it is desirable to advance the load-engaging device along the ground as in slipping a fork under a log. For this, it is necessary to rest the fork flat on the ground. In the past this has been quite difficult when the operator did not have good visibility and must operate the tilt lever by guess to control the angle of the load-engaging member. If he left it too low, it might dig into the ground. If the angle is too high, the intended load passes under the load-engaging device or may be struck by it. For example, a fork might be unable to penetrate under logs. In the case of a bucket picking up snow or other loose material on the ground or on a pavement, the ability to lie fiat on the surface is equally apparent.

According to the present invention, this difficulty is solved in a very simple and satisfactory manner by providing a valve having a float position for the tilt valve. When the valve is in this position,-the bucket or fork is free to move angularly up or down. When this feature is combined with the usual boom actuating valve which has a float position, the two cooperate. As the boom is swung down with the load-engaging device anywhere near the right position, placing the tilt valve momentarily in float position will let the device tilt up or down to place its bottom flat on the ground.

Additional objects and advantages of the invention will be apparent from the following description and from the drawing.

The drawing The drawing is a simplified side view of one form of apparatus with which the invention has been very satisfactorily used, combined with a diagrammatic representation of the main parts of the hydraulic system pertinent to the present invention.

Although the following disclosure offered for public dissemination is detailed to ensure adequacy and aid understanding, this is not intended to prejudice that purpose of a patent which is to cover each new inventive concept therein no matter how others may later disguise it by variations in form or additions or further improvements. The claim at the end hereof is intended as the chief aid toward this purpose, as it is this that meets the requirement of pointing out the parts, improvements, or combinations in which the inventive concepts are found.

Patented Oct. 29, 1968 "ice Background description The invention has been illustrated in conjunction with a reaching type of fork-lift truck. It includes a chassis 11 with front wheels 12 and rear wheels 13 both preferably driven by an engine 14. The vehicle may be provided with an operators cab but for simplicity, it has been shown with an operators seat 16 from which the operator can control the usual vehicle control devices including a steering wheel 17. Also, accessible to him is a set 18 of valve handles by which he can hydraulically control the operation of the fork device 19 or other load-engaging device.

The load-engaging device 19 is carried by a boom 21 which is pivoted at 22 to a reaching link 23, which is in turn pivoted at 24 to the chassis 11. A pair of hydraulic cylinders 26 swing the reaching link forwardly and rearwardly. As with respect to the other cylinders, only one has been shown, these cylinders being duplicated on the other side of the vehicle. A pair of lift cylinders 28 pivoted to the chassis at 29 and to the boom at 31 raises and lowers boom 21. Each lift cylinder is generally parallel to reach link 23, and when of the same length, forms a parallelogram with it so that the swinging of the reaching link does not change the angularity of boom 21 or of loadengaging device 19. This type of linkage is known as a parallelogram type of reach linkage even though it is not a true parallelogram at other lengths of cylinder 28. Of course, in speaking of the length of cylinder 28, reference is really made to the cylinder and piston combination.

The angularity of load-engaging device 19 with respect to boom 21 can be controlled by a pair of cylinders 33 pivoted to boom 21 and having piston rods 34 pivoted to the load-engaging device 19.

Actuation of piston rod 34 is controlled by a valve control handle 18-T (T standing for tilt) which actuates the spool of a valve diagrammatically represented at 36. Heretofore, this valve has been a three-position valve spring-urged toward its central position (represented diagrammatically by a section L) which would hydraulically lock the cylinder 33 against tilting movement in either direction. By moving handle 18-T rearwardly, pressure line 38 would be connected to up-tilt line 39 while down-tilt line 41 would be connected to reservoir line 42. This would actuate cylinder 33 to tilt the fork 19 upwardly and rearwardly, as represented by section U of valve 36. By operating valve handle 18-T in the forward direction from its mid position or neutral, the connections made between lines 39 and 41 and lines 38 and 42 would be reversed, as represented by section D of valve 36 so that pressure line 38 would be connected to the downtilt line 41 and up-tilt line 39 would be connected to reservoir 42. This would actuate cylinders 33 in the opposite direction to lower the fork 19.

Lift-cylinders 28 have heretofore been actuated by manual control of a similar handle 18-B which control the valve spool in a valve 43. The spool likewise has a normal position represented by section L from which it could be moved in either direction to raise or lower the boom 21. In one direction, as illustrated at section U pressure line 44 is connected to up line 46, while down line 47 is connected to reservoir line 42. In the other direction of spool movement, these connections are reversed as illustrated at section D. In addition, the boom control valves such as 43 have usually had a fourth position, represented at P, which was sometimes called a float position in that the boom 21 could settle by its own weight until the load-engaging device 19 rested on the ground. Thus, up line 46 and down line 47 are connected together and to reservoir line 42.

The present invention According to the present invention, valve 36, as well as valve 43, is provided with a fourth or float position represented by section F. Thus, when the handle 18-T is moved through one of the power conditions to an extreme position beyond it, both ends of cylinder 33 are connected to each other and to reservoir line 42. This enables fluid to move from one end of cylinder 33 to the other to enable the fork device19 to accommodate itself to the ground, angularly. Any change in the total volume of fluid within the cylinder 33 is accommodated by discharge to or drawing from reservoir line 42.

Valve 43 conventionally will stay in the float position until manually moved from it. Valve 36, however, preferably is spring-urged so that it will snap back to Lock position when no longer manually held in Float.

A preferred manner of operation is to set handle 18-B in Float. As the boom settles, the hand is removed from handle 18-B and operates handle 18-T to tilt the loadengaging device 19 to a position relative to the boom guessed to be approximately right, i.e., nearly at the right angle to be flat on'the ground when it comes down. Just as the load-engaging device 19 touches ground, or is about to, handle 18-T is operated to the Float position so that it can settle flat on the ground under the weight of the boom.

The float positions for each of valves 36 and 43 includes a constricted passage 49, to prevent a rapid fall that might be dangerous. The valves are available on the market, for example, from the Parker Hannifin Corporation, Model P-1539, for valve 43 and Model P-1540 for valve 36.

Usually the fork 19 or bucket will have so much weight well forward of the rear ground-engaging surface thereof that there ordinarily will be no danger that the weight of the boom will tip the device to raise its front toe or lip high above the ground. If necessary, a rearwardly extending heel 51 can be provided to engage the ground to the rear of the vertical plane through the pivotal axis about which the device tilts.

I claim:

1. Material handling apparatus including a mobile chassis, a boom pivotally supported by the chassis at the rear end of the boom, hydraulic lift cylinder means for raising and lowering the boom, a load-engaging device pivotally supported at the frontend of the boom having a vertically slim and generally flat bottom adapted to rest on the ground and slip under a load when advanced, bydraulie tilt cylinder means for changing the angle of the load-engaging device with respect to the boom, means for advancing the boom to advance the load-engaging device under a load, a manually controlled valve for each hydraulic cylinder means, positioned to be controlled by an operator located at a position having obstructed visibility as to the load-engaging device; each of said valves having a float position connecting the hydraulic cylinder means for freedom of movement whereby the boom may settle down and by its weight move the load-engaging device to a position flat on the ground.

No references cited.

HUGO O. SCHULZ, Primary Examiner. 

